JACKSONVILLE, Fla. -- Prosecutors say they may retry a Florida man on first-degree murder charges in the fatal shooting of a black teenager after an argument over loud music.

The trial was Florida's latest to raise questions about self-defence and race, coming six months after George Zimmerman was acquitted in the shooting of 17-year-old Trayvon Martin.

A jury convicted Michael Dunn, a 47-year-old software developer who is white, on Saturday of attempted murder for shooting into a carful of teenagers after the argument but jurors couldn't agree on the most serious charge of first-degree murder.

A mistrial was declared on that charge. State Attorney Angela Corey said her office would consider seeking a retrial.

Meanwhile, defence attorney Cory Strolla said he plans to appeal based on several issues, including how the jury could reach guilty verdicts on four counts and deadlock on another.

Dunn was charged with fatally shooting 17-year-old Jordan Davis in 2012 after the argument over loud music coming from the SUV occupied by Davis and three friends outside a Jacksonville convenience store. Dunn had described the music to his fiancee as "thug music." He claimed he acted in self-defence.

After more than 30 hours of deliberations over four days, the 12 jurors found Dunn guilty of three counts of attempted second-degree murder and a count of firing into an occupied car.

Earlier in the day, the panel said in a note to Judge Russell L. Healey that they couldn't agree on the murder charge. They also had the option of convicting him of second-degree murder or manslaughter. The judge asked them to continue their work, and they went back to the deliberation room for two more hours before returning with a verdict.

Jurors declined to talk to the media.

Dunn showed no emotion as the verdicts were read. Each attempted second-degree murder charge carries a maximum sentence of 30 years in prison, while the fourth charge he was convicted on carries a maximum of 15. A sentencing date will be set later.

Davis' parents left the courtroom in tears. Afterward his mother, Lucia McBath, expressed gratitude for the verdict. Sunday would have been the teen's 19th birthday.

"We are so grateful for the truth," McBath said. "We are so grateful that the jurors were able to understand the common sense of it all."

Jurors heard testimony that Dunn, who has a concealed weapons permit, fired 10 shots, hitting the vehicle nine times. Davis was the only person hit.

Dunn, in claiming self-defence, testified that he thought he saw a firearm pointed at him from the SUV as the argument escalated. No weapon was found in the SUV.

Dunn also told jurors he feared for his life, perceiving "this was a clear and present danger."

Prosecutors contended that Dunn opened fire because he felt disrespected by Davis. The teen made his friend turn the music back up after they initially turned it down at Dunn's request. Dunn was parked in the spot next to the SUV outside the convenience store.

According to authorities, Dunn became enraged about the music and ensuing argument. One person walking out of the convenience store said he heard Dunn say, "You are not going to talk to me like that."

Dunn testified he heard someone in the SUV shouting expletives and the word "cracker," which is a derogatory term for white people.

"That defendant didn't shoot into a carful of kids to save his life. He shot into it to save his pride," Assistant State Attorney John Guy told the jury earlier in the week. "Jordan Davis didn't have a weapon, he had a big mouth."

Phyllis Parker chants outside of the Duval County Courthouse as the jury enters the fourth day of deliberations in the trail of Michael Dunn, Saturday, Feb. 15, 2014, in Jacksonville, Fla. (AP Photo/The Florida Times-Union, Kelly Jordan)

Judge Russell Healey holds up documents as he announces that the jury is deadlocked on charge one and have verdicts in the other four charges while deliberating in the trial of Michael Dunn for the shooting death of Jordan Davis, Saturday Feb. 15, 2014. (The Florida Times-Union, Bob Mack)